The present invention relates generally to integrated circuit die removal apparatus and methods, and more particularly to die removal apparatus and methods for use with semiconductor integrated circuit devices that are attached to high density multilayer interconnect hybrid packages.
The high cost of the parent substrate and integrated circuit devices makes repair and rework of faulty multichip modules a necessity in order to reduce assembly cost and improve hybrid and multichip module yield. Successful die removal is a function of the die attach material used during assembly, the parent substrate metallization system, and the removal/repair technique utilized. A typical ceramic substrate has a gold metallization layer disposed thereon and has a semi-conductor integrated circuit device fastened thereto by a body of epoxy. This sandwich structure provides an epoxy/metallization interface, and an epoxy/device interface. Rework is relatively easy for small to moderate size integrated circuits up to about 100 mils square that are moderately spaced on ceramic substrates. Now, however, with the advent of high density multichip modules consisting of multilayer thin film substrates using thin polyimide dielectric films and thin sputtered aluminum or copper metallization, new and more difficult device attachment and rework issues have presented themselves. The polyimide dielectric films may be on the order of 5 to 15 micrometers thick, and the metallization films may be on the order of 2 to 5 micrometers thick. Additionally, spacings between semiconductor integrated circuit devices are commonly between 0.100 and 0.250 of an inch. High density multichip interconnect technology has reduced device spacing to a point where reworking of hybrids is now more difficult than ever. Spacing of high density multichip interconnect technology devices has decreased by as much as a factor of ten.
Some high density multichip interconnect substrates may incorporate as many as eight metallization layers. A substrate has a metallization layer on top of which is a polyimide layer. The polyimide layer has a metallization layer on top of it and a semiconductor integrated circuit device fastened thereto by epoxy. Typically, this type of construction is referred to as a high density multichip interconnect substrate. Unlike typical thick/thin film metallized ceramic substrates, failure of the high density multilayer interconnect substrate metallization occurs at much lower strengths. Typically, on ceramic metallization systems, failure during shear and tensile testing occurs at the epoxy/metallization interface, epoxy body, or epoxy/device interface. Failures to high density multilayer interconnect systems, however, can occur within the polyimide dielectric or at the metallization/polyimide interface, which typically has much less adhesion strength than the device attachment material, device, or substrate/epoxy interface.
There are several widely used techniques for the removal of faulty components. Four such techniques are the simple die shear technique, the dual blade die twist off technique, the tensile die pull technique, and the hot gas/tweezer technique. The transactions of the 1990 International Electronics Packaging Society (IEPS) includes a technical paper that surveys the field of removal of semiconductor integrated circuit devices from multi-chip modules. The paper discusses die shear, dual blade twist off, tensile die pull, and hot gas/tweezer techniques of die removal. The paper appears at pages 77-89, and is entitled "A Review of Repairable Die Attach For CuPI MCM". The author is Thom A. Bishop of Microelectronics and Computer Technology Corporation (MCC), 12100-A Technology Blvd., Austin, Tex. 78727. The die shear method is not useable where close proximity component spacing is encountered because of the blade interference with adjacent components and potential damage to neighboring devices from the device being removed. The dual blade die twist off removal method is not compatible with close die spacing because of blade interference with adjacent components. The die pull removal technique is quite different from the die shear and twist off method. A pull stud or peg is glued to the top of the defective die and the substrate is mounted and clamped rigidly. The stud is gripped by a second set of clamps and is pulled vertically away from the substrate. The stud and die are then removed from the substrate. Tensile pull can be performed at any temperature, substrate and die permitting, and is compatible with close die spacing.
The hot gas/tweezer removal method is a high temperature process and is not compatible with closely spaced large devices. Additionally, this technique cannot generate sufficient forces to remove large area devices using tweezers. Another disadvantage of the hot gas/tweezer method is that when large area devices (as large as 0.580 inches square) are being removed from a high density multichip module substrate, fracturing of the device, or splintering, may occur. Splintering is most apt to occur when large area devices are removed by mechanical means such as tweezers. When splintering occurs, silicon splinters become lodged between interconnects of neighboring devices.
Of the four removal methods just described, none have proven to be completely satisfactory for removing semiconductor integrated circuit devices from crowded high density multichip modules comprising multilayer thin film substrates using thin polyimide dielectric films and thin sputtered aluminum or copper metallization.
Accordingly, it would be desirable to provide a method and apparatus that is adapted to remove semiconductor integrated circuit devices from high density multilayer interconnect substrates without damage to other devices on the substrate.